Orifice or similar gas meter



oct 13,

1,556,910 T.D.CABOT @RINGE on SIMILAK GAS METER Filed June 21', 1925 2 sheets-sheet 1 @Moc/Muto Patented Oct. 13, 1925.

THOMAS D. CABOT, OIF BOSTON, MASSACHUSETTS.

ORIFICE OR SIMILAR GAS METER.

Appiicauon inea June 21, 1923. seriai No. 646,913.

Toi all w hom t may concern.'-

Be it known that I, THOMAS D. .(lnor, a citizen of the United States, residing at Boston, in the county of Suffolk and State of Massachusetts, have invented certain new and useful Improvementsin Orifice or Similar Gas Meters; and I do declare the 4following to be a full, clear, and exact description `of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to gas measuring devices, being an improved orifice meter.

At the present age, the quantity of gas passing through closed pipes for a given period of time is determined by orifice meters, Venturi and Pitot tubes, and other similar gas measuring devices from which differential pressure may be ascertained; and according to thepresent state of the art such meters are made with a differential pressure recording mechanism recording upon a graduated, clock-operated chart, and an altogether independent static pressure recording mechanism operable upon the same or another graduated, clock-operated chart. From the chart or charts, the average differential pressure and the average s-tatic pressure may be determined for a desired period of time, and from these averages, the amount of gas in cubic feet passing through the pipes for the period of time may be determined by solving the following equation:

Q Cx/LP.

In the above specified equation:

Q represents the quantity of gas in cubic feet flowing through the pipe during a given period of time.`

C representsa coefficient or constant for the particular meter, this value depending upon certain factors such as the pipe diameter, the orice diameter, the position of the pressure taps in the pipe `with respect to the orifice plate, orthe particular arrangement for ywhich the meter is calibrated, the specific gravity of the gas being measured, and the average temperature of the flowing g-as.

It represents the average differential pressure for the given period of time.'

PV represents the average absolute static pressure for the given period of time.

Of course, after the known and ascertained values have been inserted in the above specified equation, the equation may be solved in order to determine the numerical value for the s mbol Q, which represents the quantity ofy gas in cubic feet flowing through the pipe during the given period of time, by the use .of specially prepared tables. By the use of certain tables it is easier to solve the equation than it is to solve it by mathematical computation. But even to solve the equation by the use of the tables, much careful computation is necessary, so that it is the desire of those skilled in the art to have a device which will automatically lrecord factors from which the equation may be easily solved without requiring much careful computation. The present invention has been designed in order to produce such a desirable device.

The improved orifice meter rforming the subject matter of the present invention does not recoid the differential and static pressures independently,

but instead 4of this, it l,

automatically records the products of the differential and static pressures` It includes a differential pressure responsive mechanism and a static pressure responsive mechanism, but these mechanisms are coupled together and to the marker arm which operates over a graduated, clock-operated chart insuch a manner that the resultant movement of the marker will be directly proportional to the products of the differential and static pres- I i sures.

The clock-operated chart over which the marker operates may either be graduated in units representing products of differential and static pressures or in unitsrepresenting square roots of such products'. Vhere the chart is graduated inthe first mentioned units, severalreadings should be taken of values recorded at differentintervals during the period of time for which the quantity of gas passing thro-ugh the pipe is desired to be known. The square root of each reading must then be computed, and then the average of these square roots must be determined. This value must be multiplied by the constant of the meter,` and the product will be the quantity of gas in cuibic feet passing through the pipe during the given period of time. Where the chart is graduated in the last mentioned units representing square roots of products of dierential and static pressures, the average of several readings taken from it must only be multiplied by the constant of the meter in order for the quantity of gas to be determined.

p nism'of the device.

The principle of Boyles law is involved in the lsta'tic pressure., movement ori mecha As is known, one way of stating this law, is as follows The vol-V ume of a given mass-ofgas,ata constant; temperature, varies inversely as the pressure to which it is subjected The novelty in the invention resides in the combination and arrangement ofpartsV and the details of construction, which are hereinafter fully described andiclaimed,f and illustrated fin-the accompanying drawings.

InI the drawings which@ form a' part ofA thisspeciica-tion :l

FigureA .1 is a 'sidev elevation ,ofl a meter constructed in accordance withftlie princi# ples of the presentl invention;

liligure'2is,4 a top plan view 'ofl the improved metergwith the 'cover-'plate removed; and' i 'i Figures l3- and" 4 are rlongitudinal sectional r vie-ws*through-| the meter taken substantially on they planesl indicated'by the lines and A1--41respectively of'Fig. 2, tliese viewsv likegFig. 2 being drawn to' a larger scale than Fig. 1lA

In theillustrated'embodiment' of the -invention,l the numeral "1 represents -a casi-ng which is provided with four' wells 2, 3,' t and 5. The wells 2 and 3are. in communication'gwith eachotlier attheir lower ends by means of' a' passage 6, and the wells- 4f and aresimilarly in=communication with each other atv their lower'ends by means of asimilar passage '7;' Mercury or other suitable liquid 8' is placed 'in the' wells .2,r 3, et andv 5, so that' the wells 2 and: 3T and their connecting passage G forni a substantiallyv U-'slr'aped lmercury` or' liquid fool/umn,V and the wells landf5 with rtheir' connectint'g;A passage 7 form a second substantially U-shaped mercury or liquid column.

The casing 1v is providedwith" a cover 9. n

` This coverx9i-is tightly clamped onto the casing 1r so as'to be. gas-tight, a suitable gasket IO'being interposed between these two members. y A wall `11 surrounds the` well2hand entirely separates the interior ofi4 the latter, Jfrom the wellsg3, .et and Awall 12`extendslfrom the walll 11'L to vone endnof 4the. casing, passing betweentlie wells 3 and 5, but .this wall V12 is'provided with .a passage` 13'so that. gas vmay'pass from 'the chamber in'wh'icli'fthe well'3 is located'to'the chamber in'whichtlie wells' 4 andi arelocated. The` well15' is provided with closure, 141.- This 'is gas-tiglzitand'provides a gas spacev 15I in' thel u'pperportionpof thewell 5 above the mercury 8 therein. Y Tlre'cover` 9 of the' casingl' is provided with inlet` passages pllandhl'?, 'the passage lf3-pleading into' the upper porten Offthe well'f2, while thepassagej1(- "leadsfinto the upper portion ofthechamber .in whiclrthey well 3 is located. Pipes 18 and 19 lead toV means of the passage 13 with the chamberv` inl which the well' 3is disposed.

Since. upstream pressure issupplied to the well 2 and downstream pressure". to the well.

3, the substantially U-shaped mercury column. formedk by' these two wells andH their` connecting passage' may be termed adir# ferential pressure mercury column. The

downstreamv pressure which is'supplied to the' well 4' actsupon the mercury 8' .in' this well, the passage 7 Aand the well, so` as t0 compress the gas coni'ned'in'the chamber-.15

andto causethe mercury. level topindicate.k

the static pressure. c The mercury column formedtby the wells 4 and 5andtheir'connecting passage 7 may, therefore, be termed astatic pressure mercury column.

yMountedvin the casing- 1 andjextending,

transversely across oney end thereof'is apain 4of'rock-shafts .22 andv 23. Both ofthesev rock shaftsv have one'of 'their ends extending through one of the sidesv of the casing 1 to the exterior oi thecasing,stuifing boxes 24'being 'arranged in said 'sideloffthe cas-ing to preventleakage, o'fgas.

Onthe inside 'of the casingy 1, the-troekI shafts 22 and, 23.are provided/with arms,2 5.

andj26respectively,` The free end lof.: the arm 25 vis secured'to al float 27, which-flciatsj upon the mercury v8 contained "inethewell,

and the yfree endlofthe arm 26 is' secured Ato: a oat"28 which'ii'oats upon the mercury 8= contained in tlie'well 11. The outer ends of" the rock 'shafts 22 and23 are provided 'withl crank arms 29 and 30 respectively. These crank arms are arra-nged'at right angles to each other, the crank arm 29Y extendingvertically` and .the armi3() extending horizons tally.: Preferablyfthe. arm-30 is ofthe-same length as the float arm 26. y

The casing 1 ,is provided withl a. bracket 31: upon, which is mounted clockroperated chart 32. Tliiscliart is ypreferably in the.

inthe manner hereinafter described. Piv- Oted'upontlie bracket 31so as to swing.l

across the chart 32visa marker arm-33, the

free end of .wliiclifis provided witlr a .marker element 311fadapted to niark lupontlie ichartf chart moves. y

The numeral represents a\link rwhich has a slidable and vpivotal connection, `one end'to the intermediateportionof the marker arm Tlieother ,endfoflthis' llinky 35 `is pivoted to the free endaofthecrank, i

lform of a rotatable disk and. is graduated .v

arm 29 sothat a longitudinal movement will be imparted to the link 35 when thevcrank arm 29 swings; i The free end of the crank arm 30 is connected to the intermediate portion of the link 35 by means of a short link 37 so that swinging movement is imparted to the link 35 as the crank arm 30 swings. This swinging movement causes the connection 26 to slide upon the marker arm 33.

The passages 16 and 17 are provided with inwardly opening valves 38 and 39 respectively. Both of these valves are normally open. The'valve38 carries a depending stem 40, to which a float 41 is suspended. This float 41 is normally disposed above the level of the mercury in the well 2. However, when the mercury in this well rises beyond a predetermined amount, it will engage the float 41 and raise the same and cause the valve 38 to close.- The valve 39 is positioned directly above the connection between the float 27 and the float arm 25, so as `to beA engaged b-y an upwardly projecting portion ofthis connection and close in case the mercury 8 in the well 3 rises above a predetermined amount.

In assembling the device and connecting it to the pipes 18 and 19 which lead from the gas` pipe 20, a sample of the gas supplied by the pipe 20 is placed in the gas space, disposed in the upper portion of the well 5. The gas which is placed in the gas space 15 may be under normal atmospheric pressure, or undera predetermined pressure which is approximately the average working pressure in the gas pipe 20, the coefficient being suitably corrected for pressures other than atmospheric, so that the level of the mercury inthe well 5 will be the same as the level of the mercury in the well 4 at whatever pressure is predetermined. w Thus, normally the surface of the mercury inthe well 5 lies a certain distance below the lower side of the cover or closure 14. The` pivot 42 of the marker arm 33 should be locatedlso that normally it will lie the same distance below the center of the connection 36.

`Vhere the gas in the gas space 15 should be not far from atmospheric pressure, it will be suilicient for practical purposes, to fill the gas space 15 with the gas under atmospheric pressure, which canbe accomplished by screwing on the cover 14 in an atmos- "phcre of the gas. `Vhere, however, the gas pressure is much higher than atmospheric pressure, the cover 14 may be screwed on withwthe device in a chamber containing a sample of the gas under the higher pressure, or else gasunder atmospheric pressure may beentrapped in the gas space 15 as previously` described and then `*brought to the proper pressure by pouring more mercury into the well 4. Y

When gas ispassing through the gas pipe and through the orilice in the yorifice pipe 21, the gas will be under uneven pressure on opposite sides of the oriice plate '21. The upstream pressure will be exerted up-` on `the mercury in the well 2 and the downstream pressure will be exerted upon the mercury in the wells 3 and 4. The downstream pressure exerted upon the mercury in the well 3 will be less than the upstream pressure exerted upon the mercury in the well 2 so that mercury from the well.2 will pass through the passage 6 into the well 3, and the float 27 Vwill be raised.` This movement of the float 27 will swing' the fioat arm 25,rock the rock shaft 22 and swing the crank arm 29. At the same time, the gas pressure upon the mercury in the well 4 will overbalance the pressure of the gas contained inthe gas chamber 15 ofthe well, so `that mercury from the well 4 will pass through the passage 7 into the well 5. The float 28 will therefore be lowered, and in lowering it will swing the float arm 26, rock the rock shaft 23 and swing the crank arm 30. Movement of the crank arm 29 will move the link 35 longitudinally, and movement of the crank arm 30 will, throughthe medium of the link 37, move the link transversely. The connection 36 will therefore slide upon the marker arm 33 ,and the marker arm will he swung transversely across the chart 32.

The purpose of having the marker arm 33 moved by the combined movements of theV crank arms 29 and 30, or in fact. the floats 27 and 28, is to cause the marking4 element 34 carried at the free end of the marker arm to move across the chart a distance approximately in proportion to the product of the differential pressure and static pressure maintained in the gas pipe 20. It oi course' will be readily seen that the -float 27 rises in direct proportion to the differences between the upstream pressure and the downstream pressure, and that theV crank arm 29 swings in directproportion to this diferentialpressure. Thus, if the connection 36 did not slide upon the marker arm 33, the latter would swing in direct proportion to the dii:` ferential pressure. However, the connection 36 does slide upon the marker arm 33, and the amount of its movement with respect to the pivot 42 is inversely proportional t0 the static pressure. This will be readily understood when it is remembered that the arms 26 and 30, and links 37 and 35 are of such lengths and are connected together at such points that the distance between the pivot 42 of the marker arm y33 and the center of the connection 3 6 will always be maintained approximately equal to the distance of the surface of the mercury `8 in` the well 5 from the lowest side of the closure 14 of said well. These distances being maintained the same, it is easy to understand hovv theN connection 36 vslidesupon'th'e' marker armf32 in inverse proportion to the pressure to ivhicliitf'is subjected. Thus,-asf

the gas pressure upon the mercury in the Well exceeds the pressuiet'ofthe gas in :the

gasfchambery l5, the volume ofthe gas in tlie latter "will be decreased in-proportion to the ditferencefin pressure, and since the -lo'at2 281' will drop in proportion to the `decrease in volume ofthe gasinthef cha-mber 15,^the connection 36 Will beiloi'vered'i upon the marker arm33 in proportion'to tlielchfanges` yin the-static pressure.y

In order tor-the device-to operate in=tliis manner, the areas of tlie wells 4 and l5 fmusti bear tliesanie ratio as the length" ofiv the arm 30 and the rockarms-inustxbefvery close:

Sincel when gasfis flowing through the pipe^20, the connectiony36ivill be movedito the right by the differential f pressure *rei 'sponsive mechanism approxiniately'in direct proportion to the diierentiala pressure, r andy at the. same tiineyvi'illv be moved downwardly by, the static pressure-responsive ymechanism approximately in' proportionate the staticv pre'ssure-, the' resultant:l movement of the `marker element 34Cy carriedfby tlievvmarker arm 33 Will be approximately: equallto the product of 'the differentialv and -Y staticA pressures. If, therefore, fthe vchar-t 32- is fgr'a'du-c` ated in units to correspond;.Withisucliiprod ucts, the average vproduct kfor a f given length of time may be ascertained."- from-.several f supplyingidownstieain-pressure?to foneflegpfi readings. The square I root-` of this average@ must then be' determined'a-iidwy this! valueinust be multiplied, by therconstai'it ofthe? meter. y The result will thent beltliefquanftity 'of' gasy in cubi@ feet which loive'd',-

through the-pipe during the' given'periodlof:I time. If, however, thechart is graduated,V` in a Well known maniier,`in units represent ing square roots of units `which aretlie`A prod? ucts of differential andl stat-ic-l pressures, the square 'roots 'ot' products of differential land static pressures for several intervals'- during-` a given period'o/time may ,bei readfdirectly iomtlre4 chart.` Tlie average'of the'seread-Y `ings must then be determined andy this*I average must be multiplied by tlieconstant'f ofthe meter in' order to determine the Vqu antity of gas:

The a connection' 36 may carry a pointer 43 operable over a scale 44 arranged-"upon tl'iebracket3l, so that if desired, :ther staticl pressure j alone may be asceitainedll From the foregoing--descriptioii,;takenin" connection with the* accompanying' draiw.

ings, vtheconstruction,` use,floperation andV advantages of the invention` will. bereadily? understood.

It is apparent.

that various changes inI said :f differential pressure colummw a closure' y 15s-seggio:

form, proportion-, and in-f' various-details off constructionfiiiay be made Without depart-` ing :from the 1 spi-rit# and principle of'ltle in# f venti'on, orsacriicinglaiiyi oftheadvantage's-Yv thereof; and hence it is* to bei; understood? 70 that' such" changes' mayvr be2-made Witl'iin thec sc'ope'l of the appended? claims;-

Vliatisclaimed'isi .v

l, Inlay/meter of the vclass described, vtheJ l combination of aE graduated cloclr'loperaitd y75 chart,l anarmpivoted at one end andlcarry-y ingai marking velement-'- at' its othei-1` en'd to '-1 niarkv upon said chart; adiiieifential :pressureresponsive mechanism jlmov'ablel f proportionatelyf to 1 the 'differential pressurei ofthe gasV` 80' i inapipe lii'ie', aistati'c pressure responsive inecliaiiisniI movable 1 proportionately to thel' staticiv pressure ot" th'e`1gasf1in'tlieilplei-lineg'f. aflinkipivote'd at one end to said differential mechanisin and connected! intermediate* off its ends Ito the other iiieohanisim whereby" it? is moved :'longitudinallyi by onei lmechaiiis'ir'i and swungj transversely by the Iother.' mech-'2 anismy and a slidablei` anda piiotal= connection between the' other end off sa-id-y linl and f said arm, whereby tlieflattersis-I' swung'fso1 as to causel said marking elemeiitrto-i move over-said -cliartl proportionatelyto 'thee' prod# uct of the dierential fand static pressures. 'i

2. In an orifice? or: similarf "gasi meter, itliei" combination with; a-T graduated; clockoper'- ated chart,l andra marken operable ove'rsaidl chart; olmean-s forming-.impair off substam tially g U-sliaped liquid#j columns;v means*` for each column, vmeans Ifor supplying.upstream'4 pressure: to'y therotherl legfof one? colummf.- a'

closure for the other legzoatheother column', l floats' rmountedvin-wthe firstfmentioned legsV of! said columns, and yii1ea-ns:for impartinglfthe movement of? saiddloats to isaid '-inarke'r for?" movirrg the latter f over' sa-id :chamt propor-rl tionately to? thevproduct of the*dii"erential.-v and static; pressures.-

In.-:1'n=oriiic'e orl similar gas-mieter, the combination with i a graduated; cld'ckoperi ated chart; and 1a inarkerf operable over? said chart; of means forming; a@ substantially: Ufrshaped differential; pressure fliquid co-lum and a substantially.` U-'shaped :st-atie pressure-fliq-uidfcolumn, floatsffn'ioufnted in and 4neanswv for supplying downstream Apressureto one of? tli'e legs of said ycoluinns-,` m'eans: fory supply? ingf-upstreamfpifessure. to" the'A other legof* providing ra gas 1 cliamber` ati the; upperi por'- f tion of: the-other legf lsaidstatic:pressuref' column, la linkslidably and p-ivotallyt icon-` nected: tosaid marker, vand meansforfconnectingysaid-atloats to said linkin' sucheaewayi that :the resultant movement Will--move said pressures.

combination with a graduated, clock-operated chart, and a marker arm pivoted at one end to swing across said chart and carrying a marker at the other end to mark upon said chart; of a casing provided with a substantially U-shaped differential pressure liquid column and a substantially U-shaped static pressure liquid column, floats mounted in and means for supplying downstream pressure to one of the legs of each of said columns, means for supplying upstream pressure to the other leg of said diierential pressure column, a closure providing a gas chamber at the upper portion of the other leg of said static pressure column, rock? shafts mounted in said casing, loat arms carried by said rock shafts and connected to said floats, crank arms carried by said rock shafts and being arranged at right angles to each other, a link slidably and pivotally connected at one end to said marker arm and pivotally connected at its other end to one of said crank arms, and a link connecting the other crank arm with the intermediate portion of the first named link whereby the resultant movement imparted to the latter will swing said marker arm across said chart to cause said marker to move proportionately to the product of the differential and static pressures.

In testimony whereof I have hereunto aliixed my signature.

THOMAS D. CABOT. 

